Abstract
This article presents an analysis of the performance of various types of bits during rock cutting. Six types of bits, including conical (point attack) and drag bits, were tested at depths of cut ranging from 3 to 18 mm. Three force components—cutting, normal, and lateral—were measured for each experiment. The cut surface of the rock was photographed and analyzed for depth of cut and damage to the rock surface (i.e., chipping or crushing) at the conclusion of the test. The cut surface was also casted to measure rock yield, and the effect of bit geometry in regard to bit rock interaction was analyzed. The study indicated that bit geometry is the most significant parameter affecting both bit wear and cutting action. For a typical angle of attack, approximately 45°, some bits had only the bit body contacting the cutting surface, resulting in excessive bit wear, higher normal force to cutting force ratio, more crushing and less chipping of the cutting surface, and less bit penetration into the rock. Therefore, the consequences were a high specific energy consumption and a higher amount of small-size particle generation. The energy consumption for a constant depth of cut for some bit types was as high as 25 times more than that of better-designed bits, as affected by the geometry of the bit, in particular bit shape, bit tip size and angle, and arrangement of the bit body and tip.
